1. Technical Field
2. Description of the Background Art
Many machines are fitted with guards as a safety measure. For example mesh guards are fitted over moving parts of a machine. The guards have to be legitimately removed for maintenance purposes and to rectify faults and therefore have to be provided with releasable fixings. However, most usually they are provided with fixings which can be released with conventional spanners and wrenches. As a consequence non-authorized personnel can remove the guards and this may result in the guards being removed without following the best procedures as regards safety.
Nuts which require special tools to remove them are known but examples I have used having three small holes in a circular nut with which three pins of a corresponding tool co-operate have not proved satisfactory in applications involving resistance to vibration where high torque loadings are required on the nut to resist those vibrations.